Mmmmm, thats pretty galling.
Ok, longer explanation time. This is a basic Stress-strain curve (stolen shamelessly from Wikipedia)
The section of the curve between points 1 and 2 gives an area where most of the deformation will be relaxed when removing the strain from the bolt. However, as it is past the modulus of elasticity it will still retain some deformation. But here the manufacturer has determined that the residual strain and deformation is still within specifications for X number of cycles, before it shifts past the elastic limit of the bolt. Each time the bolt is torqued it will retain more strain until it is eventually useless for their purposes. But being able to work within the elastic to proportional limits allows for a bit of wiggle room and therefore better serviceability.
All of this, however, is far beyond what your average two left handed no thumbs shifting spanner user will do.
